Hot water heater



D. J. M LAREN HOT WATER HEATER Feb. 3, 1970 Filed Sept. 12, 1967INVENTOR fl g/0 .l Mdnmw gw fil er-0e s United States Patent 3,492,972HOT WATER HEATER David J. McLaren, Bradley, 11]., assignor to A. O.Smith Corporation, Milwaukee, Wis., a corporation of New York FiledSept. 12, 1967, Ser; No. 667,126 Int. Cl. F24h 1/18 US. Cl. 122--17 8Claims ABSTRACT OF THE DISCLOSURE The conventional gas-fired waterheater includes a central flue which extends upwardly through the tankand the gases of combustion pass upwardly within the flue so that heatwill be transferred from the combustion gases to the water within thetank.

In a hot water heater, the heated water tends to stratify in the tankwith the highest temperature water being located at the top. When thehigh temperature wafer is drawn from the top of the tank, cold water issimultaneously supplied to the bottom and as the cold water enters, thetemperature in the lower portion of the tank falls way below thethermostat setting with the result that the thermostat will actuate thegas burner to heat the water within the tank. When the temperature ofthe water has regained he thermostat setting, the burner is shut off.

It has been found that when a series of intermittent, relatively shortdraws of hot water are made, each draw may cause a suflicient volume ofcold water to enter the tank to actuate the burner, and the heated waterat the tOp of the tank will be further heated by the gases of combustionpassing within the flue so that in some cases the water at the top ofthe tank may be heated 30 to 40 F. above the thermostat setting. Whenthis overheated water is drawn from the tank, there is a danger ofburning and scalding the user. In addition, the conventional hot waterheater includes a pressure and temperature relief valve and theoverheated water in the top of the tank may exceed he setting of therelief valve thereby causing a discharge of heated water from the upperend of the tank to relieve the excess temperature. This relief of thehigh temperature water not only is a waste of heated water, but can be anuisance factor if the relief valve is not piped to a drain.

The present invention is directed to an improved gasfired water heaterwhich eliminates the problem of overheating of the water in the upperportion of the tank. According to the invention, the upper portion ofthe flue within the tank is insulated, thereby reducing the heattransfer from the combustion gases passing within the flue to the waterin the upper portion of the tank. In the preferred form of theinvention, a tubular sleeve is disposed within the upper end of the flueand spaced inwardly of the flue to provide 'an annular space or gaptherebetween. A baffie is located within the sleeve and projectsdownwardly beyond the sleeve to the lower end of the flue. The upper endof the baffle, within the sleeve, is generally straight without surfacedeviations, while the lower end of the baflle, located within the fluebeneath the sleeve, is spiral in shape. As the flue gases pass upwardlywithin the flue, the spiral lower portion of the baffle serves "ice toprovide a turbulent flow for the flue gas to thereby increase the rateof heat transfer from the flue gases to the water in the lower end ofthe tank. The upper straight portion of the baffle, however, minimizesturbulence of the combustion gases and therefore tends to reduce heattransfer between the combustion gases and the water in the upper end ofthe tank. Thus, the configuration of the bafile acts in conjunction withthe dead air space around the upper end of the flue to provide aninsulating efiect which reduces heat transfer to the water in the upperend of the tank and thereby prevents overheating.

With the structure of the invention, the water in the upper end of thetank will not be overheated, even when short intermittent draws aremade. By reducing the tendency for overheating, the potential danger ofburning or scalding is eliminated and the unnecessary relief of hightemperature water through the pressure and temperature relief valve isalso avoided.

Other objects and advantages will appear in the course of the followingdescription:

The drawings illustrate the best mode presently contemplated of carryingout the invention.

In the drawings:

FIG. 1 is a vertical section of a typical gas-fired water heaterincorporating the invention;

FIG. 2 is a transverse section taken along line 22 of FIG. 1; and

FIG. 3 is a transverse section taken along line 33 of FIG. 1.

The drawings illustrate a conventional gas-fired water heater includinga tank 1 which is located within an outer casing 2 and a layer of heatinsulating material 3 is located within the space between the tank 1 andthe outer casing 2. The tank 1 includes a generally cylindrical shell 4with the upper end of the shell being enclosed by an upper head 5 andthe lower end of the shell being euclosed by generally convex lower head6. Extending downwardly from lower head 6 in a generally cylindricalskirt 7 which defines a burner compartment 8 and the lower end of theburner compartment is closed off by a base plate 9 supported on legs 10.

The water contained within the tank 1 is heated by a conventionalgas-fired burner 11 which is located within burner compartment 8. Gas issupplied to the burner 11 through a gas pipe 12 and the flow of gaswithin the line 9 is controlled by a solenoid operated gas valve 13. Athermostat 14 is located in the lower portion of the tank 1 and isresponsive to the temperature of water therein. The thermostat 14 isoperably connected to valve 13 and serves to modulate the flo-w of gasto the burner 11 in response to the demand for heat, or to turn the flowof gas on or off in response to the demand for heat, depending on thetype of heater used.

The gases of combustion are conducted upwardly through a flue 15 whichis located centrally of the tank 1 and is secured within openings in theupper head 5 and the lower head 6.

Heated water in the upper end of the tank is discharged through anoutlet pipe 16 which is threaded within a stud 17 welded within anopening in the upper head 5. To supply cold water to the tank, an inletpipe 18 is threaded within a stud 19 in upper head 5, and a dip tube 20communicates with the inlet pipe 18 and extends downwardly to a distanceslightly above the lower head 6.

The heated water in tank 1 will tend to stratify, with the water in theupper end of the tank being at the highest temperature. When heatedwater is drawn through the outlet pipe 16, a corresponding volume ofcold water will be introduced to the tank through the dip tube 20, andwhen the temperature in the lower end of the tank falls below thesetting of the thermostat 14, the gas valve 13 will open to admit gas tothe burner 11. When the burner is operating, the gases of combustionpass upwardly within the flue 15 and tend to heat the water within thetank. It has been found that when short, intermittent draws of water aremade, the water in the upper end of the tank will tend to overheat dueto heat transfer from the flue gases when the burner operates during thedraw periods. To prevent this overheating, a sleeve 21 is disposedwithin the upper portion of the flue 15 and the upper end of the sleeve21 is provided with a flange 22 which is secured to the upper end of theflue. The sleeve 21 is spaced inwardly of the flue 15 to provide anannular space 23 between the members. As the space 23 is closed at itsupper end due to the connection between the sleeve and the flue, therewill be no appreciable gas flow within the space and the space willserve as a heat insulating barrier between the flue gases and the waterin the upper end of the tank 1.

The sleeve 21 can be formed of any desired material which will withstandthe temperatures involved, such as asbestos, ceramic materials, metal orthe like.

In addition to sleeve 21, a baffle 24 is mounted within the flue 15. Theupper end 25 of the baffle is secured to the upper end of the sleeve 21so that the sleeve and baflle can be inserted and withdrawn from theflue 15 as an intgral unit. As shown in FIG. 1, the upper end 25 of thebaflle, within sleeve 21, is generally straight, without any surfacedeviations, while the lower end 26 of the baffle, which is locatedbeneath the sleeve 21, has a generally spiral configuration. As thegases of combustion pass upwardly within the flue 15, the spiral portion26 of the baflle will tend to provide a relatively turbulent gas flowwhich will increase the rate of heat transfer between the combustiongases and the water in the lower end of the tank. However, the upper,straight portion 25 of the baflie 24 will minimize the turbulence of thegas and thereby tend to reduce the heat transfer from the combustiongases to the sleeve 21, as well as to the water in the upper portion ofthe tank. Thus, the baflie 2.4 cooperates with the sleeve 21 to increasethe rate of heat transfer to the water in the lower portion of the tankwhile reducing the rate of heat transfer to the water in the upperportion of the tank.

With the structure of the invention, the water in the upper end of thetank will not be overheated even when short intermittent draws are made.By reducing the tendency for overheating, the potential danger ofscalding and burning of the user is decreased. Moreover, as the water inthe upper end of the tank will not be overheated, the unnecessary reliefof high temperature water through the pressure and temperature reliefvalve is avoided.

While the present invention shows the use of a sleeve 21 in the upperend of the flue 15 to provide a heat insulating barrier therebetween, itis contemplated that other insulating means can be applied to the upperend of the flue. For example, a high temperature insulating materialwhich will not decompose or deteriorate when subjected to the hightemperatures of the water or the flue gases can be applied as a coatingto either the inner or outer surface of the upper end of the flue, or toboth surfaces.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. In a hot water heater, a tank to contain heated water and includingan upper head having a cold water inlet and having a hot water outlet inthe upper head, gas heating means located beneath the tank for heatingthe water within the tank, a flue extending upwardly from said gasheating means to the upper head and arranged to conduct the gases ofcombustion, the lower end portion of the flue being in direct heattransfer relation to the water in the lower end portion of the tank, atubular sleeve disposed within the flue in radially spaced relation tothe upper end portion of the flue and extending downwardly a substantialdistance from the upper head to provide an annular space between thesleeve and the flue, the upper end of the sleeve being connected to theflue to close off the upper portion of said annular space and the bottomend of said annular space being open, said annular space serving as adead gas space and acting as a heat insulating barrier to reduce therate of heat transfer from the combustion gases to the water in theupper end portion of the tank.

2. The hot water heater of claim 1, wherein the flue extends generallycentrally of the tank, and projects through an opening in the upperhead.

3. The hot water heater of claim 1, and including means located withinthe lower portion of the flue to increase the turbulence of thecombustion gases therein and thereby increase the rate of heat transferfrom the combustion gases to the water located in the lower end portionof the tank.

4. The hot water heater of claim 1, wherein said last named means is aspirally arranged baflle disposed within said flue.

5. A hot water heater, comprising a tank to contain heated water andhaving a cold water inlet and having a hot water .outlet in the upperend, a gas fired burner located beneath the tank for heating the waterin the tank, a flue extending upwardly from the burner to the top of thetank, heat insulating means associated with the upper portion of theflue for reducing heat transfer from the combustion gases to the waterin the upper end portion of the tank, and baflle means disposed withinthe flue, the upper portion of said baflie means located radiallyinwardly of said heat insulating means being generally straight and thelower portion of said baflle means located beneath said heat insulatingmeans being provided with surface deviations to increase the turbulenceof flow of the combustion gases within said lower portion of the fluemeans and thereby increase the rate of heat transfer from the combustiongases to the water in the lower portion of the tank.

6. The hot water heater of claim 5, wherein said heat insulating meanscomprises a separate tubular sleeve spaced radially from said flue toprovide an annular space therebetween.

7. The hot water heater of claim 6, and including means for securingsaid sleeve to the flue, said means extending circumferentially withinsaid anular space to close said space and prevent free longitudinal flowof the combustion gases within said space.

8. The hot water heater of claim 6, wherein the upper end of said bafflemeans is attached to the sleeve whereby said sleeve and said bafllemeans can be inserted and withdrawn from said flue as a unit.

References Cited UNITED STATES PATENTS 192,010 6/1877 Rice et a1 122-164299,003 5/1884 Patton 122-164 218,393 8/1879 Miller 122l64 1,077,16010/1913 Reese. 2,684,054 7/1954 Carson 122-17 3,266,485 8/1966 Girton l26360 FREDERICK L. MATTESON, IR., 'Primary Examiner R. A. DUA, AssistantExaminer US. Cl. X.R. l22164

